1. Field of the Invention
This invention relates to the cutting of vegetation, and more particularly, it relates to the cutting of vegetation using a flexible, non-metallic cutting line extending from a rotating head into a cutting plane.
2. Description of Prior Art
Various types of devices have been proposed for many years to facilitate the removal of vegetation by mowing, trimming, edging and like cutting operations. In general, these devices have employed a metal blade to effect vegetation removal. Devices of this nature employ prime movers such as electric and gasoline motors. As a result, rotating metal blades can inflict serious and terrible injury upon the user.
In the United States of America, practical vegetation cutting devices using flexible, non-metallic lines carried upon a rotating head were developed. Examples of these devices are shown in U.S. Pat. Nos. 3,708,967, 3,826,068, 4,052,789, 4,054,992, 4,067,108 and 4,104,797. These patented devices have met outstanding success in that these American developments provide safer electrical or gasoline-powered tools for vegetation cutting, edging and trimming operations.
The devices shown in these patents employ a flexible cutting line, such as manufactured from Nylon.RTM. polymer. The cutting line is carried usually upon a spool internally of a rotating head. When desired to replenish the line or to extend an additional length of it, the rotation of the head was stopped and line manually extended from the spool. This line extension procedure in the patented devices has been found to be convenient, simple and reliable. In many of the more powerful devices, especially those powered by DC electric motors, a system to extend the cutting line from the head without interrupting cutting operations was desired.
A most desirable system would be capable of feeding automatically cutting line as needed from the spool and without the action of the operator. Structures directed toward this purpose are shown in U.S. Pat. Nos. 3,895,440, 4,020,550 and 4,035,915. These structures have in common a basket-weave supply of cutting line carried on the periphery of a disc with the line feeding from behind special post members. These post members have a cutting-abrading edge so that cutting line from the weave supply is bent about such edge in the free traveling end portion extending into the cutting plane. The combination function of the edge, line, angular speed, etc., is arranged so that the line posts with such edge sever the free end of the cutting line when it is worn to an ineffective length. In practice, these structures are found to waste about 25 percent of the cutting line because of the excessive length of line severed at the post's edge, e.g., three inches.
Other line feeding structures are shown in U.S. Pat. Nos. 4,118,864 and 4,138,810. These mechanisms control spool rotation in line feeding functions by worm and spur gears having complex action in the vegetation cutting environment. Another line feeding mechanism is shown in U.S. Pat. No. 4,104,796 wherein speed sensitive cams control rotation of a spool within a cutting head.
The present invention provides a rotating head with a simple mechanism that maintains the cutting line at its maximum present length in the cutting plane irrespective of rates of cutting line wear or loss and without interrupting vegetation cutting or requiring independent operation action. However, the operator can selectively activate the mechanism if additional lengths of cutting line extensions are desired.